Your gun appears to be a "Presentation" grade sometimes called Exhibition or Special grade. I don't see any descrepancy because of the engraving on the tang. These are the very highest quality Greeners built. I can't see the engraving well enough to tell if it is an Imperial or a higher grade. My guess is that you have an F-70 Imperial or possibly an F-90. The serial number indicates the first gun of 196 guns built in 1930. At any rate you have a very nice Greener and I'm guessing very proud to own it.
Jim
